Acoustically induced optical effects in Pr~(3+) and Tm~(3+) doped calcium gadolinium oxyborate nanocomposites

摘要

Acoustically induced two-photon absorption (AITPA) and optical Kerr effect (AIOKE) in Pr and Tm doped calcium gadolinium oxyborate Ca_4GdO(BO_3)_3 (CGOB) nanocrystallites (with sizes below 60 nm) prepared by sol-gel method and embedded into the PMMA matrices were studied. The source of the acoustical field generated the frequency equal to about 1.2 MHz and achieved maximal acoustical power density equal to about 6W/cm~2. The AITPA was measured at fundamental Englass laser wavelength (1.54 (ìm) and was observed only during applying of the prolonged acoustical field. The AITPA effect was substantially higher for the Tm~(3+) doped composites than for the Pr~(3+) doped ones. With increasing acoustical power, the AITPA increases achieving its maximal value at acoustical power density equal to about 4.70 W/cm2. Temperature dependences have demonstrated the maximal values of the AITPA at temperatures equal to about 310 K corresponding to the AITPA value equal to about 3.4 cm/GW. At the same time at acoustical power density about 3.8 W/cm2 the AIOKE achieves its minimum for the Pr doped CGOB nanocomposites. So one can expect that these two effects have different signs of contribution caused by the acoustical field.